1. Field of the Invention
The present invention is related to a booster including a charge pumping circuit. More particularly, the present invention is related to a booster which includes a charge pumping circuit and can reduce its electric power consumption.
2. Description of the Related Art
A booster including a charge pumping circuit is widely used in semiconductor apparatuses. A conventional booster is disclosed in Japan Laid Open Patent Application (JP-A-Heisei, 1-241659). The conventional booster has a switching circuit as shown in FIG. 1. The switching circuit 201 generates a clock signal CIN from a standard clock signal CLK, and sends it through a clock driver 202 to a charge pumping circuit 203. A frequency of the clock signal CIN is switched on the basis of whether the semiconductor apparatus including the booster is in a standby mode or a normal operation mode. The charge pumping circuit 203 boosts a voltage V.sub.IN inputted from an input terminal. The charge pumping circuit 203 generates a voltage V.sub.OUT higher than the voltage V.sub.IN and further outputs the voltage V.sub.IN from an output terminal. The clock signal CIN is used to boost the voltage V.sub.IN to the voltage V.sub.OUT.
The switching circuit 201 has a 1/n divider 204 and a selector 205, as shown in FIG. 2. The 1/n divider 204 is provided with dividers 206 to 209. The selector 205 is provided with an inverter 210, AND gates 211, 212 and an OR gate 213.
The switching circuit 201 operates differently depending on whether the semiconductor apparatus is in the normal operation mode or the standby mode. At a time of the normal operation mode, the switching circuit 201 outputs the standard clock signal CLK as the clock signal CIN. At a time of the standby mode, the switching circuit 201 outputs a clock signal in which a standard clock signal is divided by 1/n at the time of the standby mode, as the clock signal CIN.
Incidentally, other boosters are disclosed in Japan Laid Open Patent Application (JP-A-Showa 64-39263, JP-A-Heisei 5-64429, JP-A-Heisei 7-160215, JP-A-Heisei 7-226078, JP-A-Heisei 10-304653 and JP-A-Heisei 10-304654).
The conventional booster consumes large electric power at the time of the normal operation. This is because the conventional booster always sends a signal having the same frequency as the standard clock signal CLK to the charge pumping circuit, as the clock signal CIN at the time of the normal operation. A booster is desired in which the electric power consumption is reduced at the time of the normal operation.
Also, the conventional booster is large in variation of an output voltage. This is because the output voltage is not controlled. A booster is desired in which the variation of the output voltage is small.